Flow control valves are a well-known and integral part of most irrigation systems. A typical example can be seen in U.S. Pat. No. 6,394,413 to Lohde et al., hereby incorporated by reference.
These valves control the flow of water through an upstream pipe and thereby turn sprinklers fed by the pipe on and off. Such valves are usually remotely actuated by control signals sent from an automated irrigation controller. Often these control signals are electric current sent from the controller to a solenoid in the valve which ultimately controls whether the valve is open or closed.
Solenoid-activated diaphragm-operated valves for use in irritation systems are well known. One example can be seen in U.S. Pat. No. 6,394,413 to Lohde et al., previously incorporated by reference.
This style of valve has a closure member with a sealing surface which moves against or away from an annular seat to close or open the valve. Integral to the closure member is a diaphragm positioned to seal off an upper portion of the valve. When the valve is to be opened, the fluid pressure is relieved by bleeding fluid out of the diaphragm chamber through a manual valve or a remotely operated solenoid valve. Relieving this pressure allows the closure member to move upwards as water passes through the valve. The discharged water is most conveniently released into the passageway, beyond the primary flow-controlling sealing member, near the outlet port. This design is commonly referred to as “internal bleed” offering the advantage that no water is discharged outside the fluid path.
A typical style of valve, of interest in this invention, is constructed of PVC (polyvinyl chloride plastic). One type has inlet and outlet that will accept standard threaded fittings. These require an additional fitting to create the threaded joint with PVC pipe. Another valve fitting design called a slip fit will accept PVC pipe directly, being fastened with suitable solvent-based glue.
Solenoid valve installation into an irrigation system typically involves applying a primer to the end of a pipe (such as a PVC pipe), then coating the outer end surface of the pipe and possibly the inner surface of the valve fitting, with glue (e.g., PVC glue). Finally, the end of the pipe is inserted into the water inlet port. The same process is repeated for the water outlet port of the valve.
Ideally, an appropriate amount of glue is applied to the pipe and therefore remains only between the pipe and the fitting for the pipe. However, it can be difficult to determine the appropriate amount of glue for installation. Therefore, contractors will frequently apply excess glue to both coated surfaces.
This excess glue is often pushed or expelled on to the inner surfaces of the valve. When a pipe is inserted into the water outlet port, the glue can inadvertently cover the discharge passage of the discharge port. The discharge port allows the solenoid to relieve pressure in the diaphragm chamber and therefore open the valve to water flow. Thus, the solenoid is unable to release water from the diaphragm chamber when the discharge passage is blocked by glue, thereby preventing the valve from opening.